I have heard this before and I find it surprising, as I once spilled the bubbles in the mixed-epoxy and ended up with much arm-wrestling with what turned out to be a stiff rubbery harder-than-dough type substance. It was way too thick but after some rolling long pieces of it between my warm palms it was barely useable. Heh, it kinda weighed in around, oooo, NOTHING !!

So why do they need a high-shear mixer to do this ?

S

not high shear ,high speed mixer and they mix it hot

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This is my opinion of these facts and only my opinion, your opinion may vary

Lynn Erickson A&P for lets say almost 30 years
Much better with a Dremel than a computer.
What if they gave me choice between a fast computer or a fast plane?